<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/drivers/usb/gadget/function/u_ether.c, branch v6.9</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>usb: gadget: constify the struct device_type usage</title>
<updated>2024-02-19T08:35:46+00:00</updated>
<author>
<name>Ricardo B. Marliere</name>
<email>ricardo@marliere.net</email>
</author>
<published>2024-02-18T19:18:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=3e383260dfd406d8bb09a64cadeafb5cd71a7e0c'/>
<id>3e383260dfd406d8bb09a64cadeafb5cd71a7e0c</id>
<content type='text'>
Since commit aed65af1cc2f ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the gadget_type
variable to be a constant structure as well, placing it into read-only
memory which can not be modified at runtime.

Signed-off-by: Ricardo B. Marliere &lt;ricardo@marliere.net&gt;
Link: https://lore.kernel.org/r/20240218-device_cleanup-usb-v1-3-77423c4da262@marliere.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Since commit aed65af1cc2f ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the gadget_type
variable to be a constant structure as well, placing it into read-only
memory which can not be modified at runtime.

Signed-off-by: Ricardo B. Marliere &lt;ricardo@marliere.net&gt;
Link: https://lore.kernel.org/r/20240218-device_cleanup-usb-v1-3-77423c4da262@marliere.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Re-attach netif device to mirror detachment</title>
<updated>2024-01-04T15:04:28+00:00</updated>
<author>
<name>Richard Acayan</name>
<email>mailingradian@gmail.com</email>
</author>
<published>2023-12-18T16:45:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=76c945730cdffb572c7767073cc6515fd3f646b4'/>
<id>76c945730cdffb572c7767073cc6515fd3f646b4</id>
<content type='text'>
In 6.7-rc1, there was a netif_device_detach call added to the
gether_disconnect function. This clears the __LINK_STATE_PRESENT bit of
the netif device and suppresses pings (ICMP messages) and TCP connection
requests from the connected host. If userspace temporarily disconnects
the gadget, such as by temporarily removing configuration in the gadget
configfs interface, network activity should continue to be processed
when the gadget is re-connected. Mirror the netif_device_detach call
with a netif_device_attach call in gether_connect to fix re-connecting
gadgets.

Link: https://gitlab.com/postmarketOS/pmaports/-/tree/6002e51b7090aeeb42947e0ca7ec22278d7227d0/main/postmarketos-base-ui/rootfs-usr-lib-NetworkManager-dispatcher.d-50-tethering.sh
Cc: stable &lt;stable@kernel.org&gt;
Fixes: f49449fbc21e ("usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach")
Signed-off-by: Richard Acayan &lt;mailingradian@gmail.com&gt;
Tested-by: Luca Weiss &lt;luca@z3ntu.xyz&gt;
Tested-by: Duje Mihanović &lt;duje.mihanovic@skole.hr&gt;
Link: https://lore.kernel.org/r/20231218164532.411125-2-mailingradian@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In 6.7-rc1, there was a netif_device_detach call added to the
gether_disconnect function. This clears the __LINK_STATE_PRESENT bit of
the netif device and suppresses pings (ICMP messages) and TCP connection
requests from the connected host. If userspace temporarily disconnects
the gadget, such as by temporarily removing configuration in the gadget
configfs interface, network activity should continue to be processed
when the gadget is re-connected. Mirror the netif_device_detach call
with a netif_device_attach call in gether_connect to fix re-connecting
gadgets.

Link: https://gitlab.com/postmarketOS/pmaports/-/tree/6002e51b7090aeeb42947e0ca7ec22278d7227d0/main/postmarketos-base-ui/rootfs-usr-lib-NetworkManager-dispatcher.d-50-tethering.sh
Cc: stable &lt;stable@kernel.org&gt;
Fixes: f49449fbc21e ("usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach")
Signed-off-by: Richard Acayan &lt;mailingradian@gmail.com&gt;
Tested-by: Luca Weiss &lt;luca@z3ntu.xyz&gt;
Tested-by: Duje Mihanović &lt;duje.mihanovic@skole.hr&gt;
Link: https://lore.kernel.org/r/20231218164532.411125-2-mailingradian@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach</title>
<updated>2023-10-08T05:50:36+00:00</updated>
<author>
<name>Hardik Gajjar</name>
<email>hgajjar@de.adit-jv.com</email>
</author>
<published>2023-10-06T15:56:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f49449fbc21e7e9550a5203902d69c8ae7dfd918'/>
<id>f49449fbc21e7e9550a5203902d69c8ae7dfd918</id>
<content type='text'>
This patch replaces the usage of netif_stop_queue with netif_device_detach
in the u_ether driver. The netif_device_detach function not only stops all
tx queues by calling netif_tx_stop_all_queues but also marks the device as
removed by clearing the __LINK_STATE_PRESENT bit.

This change helps notify user space about the disconnection of the device
more effectively, compared to netif_stop_queue, which only stops a single
transmit queue.

Signed-off-by: Hardik Gajjar &lt;hgajjar@de.adit-jv.com&gt;
Link: https://lore.kernel.org/r/20231006155646.12938-1-hgajjar@de.adit-jv.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This patch replaces the usage of netif_stop_queue with netif_device_detach
in the u_ether driver. The netif_device_detach function not only stops all
tx queues by calling netif_tx_stop_all_queues but also marks the device as
removed by clearing the __LINK_STATE_PRESENT bit.

This change helps notify user space about the disconnection of the device
more effectively, compared to netif_stop_queue, which only stops a single
transmit queue.

Signed-off-by: Hardik Gajjar &lt;hgajjar@de.adit-jv.com&gt;
Link: https://lore.kernel.org/r/20231006155646.12938-1-hgajjar@de.adit-jv.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: use working speed to calcaulate network bitrate and qlen</title>
<updated>2023-08-22T12:48:33+00:00</updated>
<author>
<name>Linyu Yuan</name>
<email>quic_linyyuan@quicinc.com</email>
</author>
<published>2023-08-03T09:10:47+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=98102ae1549e3af33359ec3a8e57adafa57b1b01'/>
<id>98102ae1549e3af33359ec3a8e57adafa57b1b01</id>
<content type='text'>
Take ecm_bitrate() as example, it will be called after gadget device
link speed negotiation, consider code
if (gadget_is_superspeed(g) &amp;&amp; g-&gt;speed == USB_SPEED_SUPER),
if a gadget device link speed is USB_SPEED_SUPER,
gadget_is_superspeed(g) must be true, or not it is a wrong
configuration of gadget max support speed.

Remove gadget_is_superspeed(g) checking should be safe, and remove other
similar operation in ncm, rndis, u_ether.

Signed-off-by: Linyu Yuan &lt;quic_linyyuan@quicinc.com&gt;
Link: https://lore.kernel.org/r/20230803091053.9714-2-quic_linyyuan@quicinc.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Take ecm_bitrate() as example, it will be called after gadget device
link speed negotiation, consider code
if (gadget_is_superspeed(g) &amp;&amp; g-&gt;speed == USB_SPEED_SUPER),
if a gadget device link speed is USB_SPEED_SUPER,
gadget_is_superspeed(g) must be true, or not it is a wrong
configuration of gadget max support speed.

Remove gadget_is_superspeed(g) checking should be safe, and remove other
similar operation in ncm, rndis, u_ether.

Signed-off-by: Linyu Yuan &lt;quic_linyyuan@quicinc.com&gt;
Link: https://lore.kernel.org/r/20230803091053.9714-2-quic_linyyuan@quicinc.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Fix host MAC address case</title>
<updated>2023-05-13T09:46:59+00:00</updated>
<author>
<name>Konrad Gräfe</name>
<email>k.graefe@gateware.de</email>
</author>
<published>2023-05-05T14:36:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=3c0f4f09c063e143822393d99cb2b19a85451c07'/>
<id>3c0f4f09c063e143822393d99cb2b19a85451c07</id>
<content type='text'>
The CDC-ECM specification [1] requires to send the host MAC address as
an uppercase hexadecimal string in chapter "5.4 Ethernet Networking
Functional Descriptor":
    The Unicode character is chosen from the set of values 30h through
    39h and 41h through 46h (0-9 and A-F).

However, snprintf(.., "%pm", ..) generates a lowercase MAC address
string. While most host drivers are tolerant to this, UsbNcm.sys on
Windows 10 is not. Instead it uses a different MAC address with all
bytes set to zero including and after the first byte containing a
lowercase letter. On Windows 11 Microsoft fixed it, but apparently they
did not backport the fix.

This change fixes the issue by upper-casing the MAC to comply with the
specification.

[1]: https://www.usb.org/document-library/class-definitions-communication-devices-12, file ECM120.pdf

Fixes: bcd4a1c40bee ("usb: gadget: u_ether: construct with default values and add setters/getters")
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Gräfe &lt;k.graefe@gateware.de&gt;
Link: https://lore.kernel.org/r/20230505143640.443014-1-k.graefe@gateware.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The CDC-ECM specification [1] requires to send the host MAC address as
an uppercase hexadecimal string in chapter "5.4 Ethernet Networking
Functional Descriptor":
    The Unicode character is chosen from the set of values 30h through
    39h and 41h through 46h (0-9 and A-F).

However, snprintf(.., "%pm", ..) generates a lowercase MAC address
string. While most host drivers are tolerant to this, UsbNcm.sys on
Windows 10 is not. Instead it uses a different MAC address with all
bytes set to zero including and after the first byte containing a
lowercase letter. On Windows 11 Microsoft fixed it, but apparently they
did not backport the fix.

This change fixes the issue by upper-casing the MAC to comply with the
specification.

[1]: https://www.usb.org/document-library/class-definitions-communication-devices-12, file ECM120.pdf

Fixes: bcd4a1c40bee ("usb: gadget: u_ether: construct with default values and add setters/getters")
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Gräfe &lt;k.graefe@gateware.de&gt;
Link: https://lore.kernel.org/r/20230505143640.443014-1-k.graefe@gateware.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: f_ecm: Add suspend/resume and remote wakeup support</title>
<updated>2023-03-29T08:27:01+00:00</updated>
<author>
<name>Elson Roy Serrao</name>
<email>quic_eserrao@quicinc.com</email>
</author>
<published>2023-03-24T21:48:02+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0a1af6dfa0772ffedaef422127f1338fa0ddfed3'/>
<id>0a1af6dfa0772ffedaef422127f1338fa0ddfed3</id>
<content type='text'>
When host sends suspend notification to the device, handle
the suspend callbacks in the function driver. Depending on
the remote wakeup capability the device can either trigger a
remote wakeup or wait for the host initiated resume to resume
data transfer.

Signed-off-by: Elson Roy Serrao &lt;quic_eserrao@quicinc.com&gt;
Reviewed-by: Thinh Nguyen &lt;Thinh.Nguyen@synopsys.com&gt;
Link: https://lore.kernel.org/r/1679694482-16430-7-git-send-email-quic_eserrao@quicinc.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When host sends suspend notification to the device, handle
the suspend callbacks in the function driver. Depending on
the remote wakeup capability the device can either trigger a
remote wakeup or wait for the host initiated resume to resume
data transfer.

Signed-off-by: Elson Roy Serrao &lt;quic_eserrao@quicinc.com&gt;
Reviewed-by: Thinh Nguyen &lt;Thinh.Nguyen@synopsys.com&gt;
Link: https://lore.kernel.org/r/1679694482-16430-7-git-send-email-quic_eserrao@quicinc.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Don't warn in gether_setup_name_default()</title>
<updated>2023-02-15T11:36:22+00:00</updated>
<author>
<name>Jon Hunter</name>
<email>jonathanh@nvidia.com</email>
</author>
<published>2023-02-09T12:53:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=19ac99072e679f1e3807603206e3f3b1a7c14729'/>
<id>19ac99072e679f1e3807603206e3f3b1a7c14729</id>
<content type='text'>
The function gether_setup_name_default() is called by various USB
ethernet gadget drivers. Calling this function will select a random
host and device MAC addresses. A properly working driver should be
silent and not warn the user about default MAC addresses selection.
Given that the MAC addresses are also printed when the function
gether_register_netdev() is called, remove these unnecessary warnings.

Signed-off-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Reviewed-by: Andrzej Pietrasiewicz &lt;andrzej.p@collabora.com&gt;
Link: https://lore.kernel.org/r/20230209125319.18589-2-jonathanh@nvidia.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The function gether_setup_name_default() is called by various USB
ethernet gadget drivers. Calling this function will select a random
host and device MAC addresses. A properly working driver should be
silent and not warn the user about default MAC addresses selection.
Given that the MAC addresses are also printed when the function
gether_register_netdev() is called, remove these unnecessary warnings.

Signed-off-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Reviewed-by: Andrzej Pietrasiewicz &lt;andrzej.p@collabora.com&gt;
Link: https://lore.kernel.org/r/20230209125319.18589-2-jonathanh@nvidia.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Convert prints to device prints</title>
<updated>2023-02-15T11:36:22+00:00</updated>
<author>
<name>Jon Hunter</name>
<email>jonathanh@nvidia.com</email>
</author>
<published>2023-02-09T12:53:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=938fc645317632d79c048608689683b5437496ea'/>
<id>938fc645317632d79c048608689683b5437496ea</id>
<content type='text'>
The USB ethernet gadget driver implements its own print macros which
call printk. Device drivers should use the device prints that print the
device name. Fortunately, the same macro names are defined in the header
file 'linux/usb/composite.h' and these use the device prints. Therefore,
remove the local definitions in the USB ethernet gadget driver and use
those in 'linux/usb/composite.h'. The only difference is that now the
device name is printed instead of the ethernet interface name.

Tested using ethernet gadget on Jetson AGX Orin.

Signed-off-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Tested-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Link: https://lore.kernel.org/r/20230209125319.18589-1-jonathanh@nvidia.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The USB ethernet gadget driver implements its own print macros which
call printk. Device drivers should use the device prints that print the
device name. Fortunately, the same macro names are defined in the header
file 'linux/usb/composite.h' and these use the device prints. Therefore,
remove the local definitions in the USB ethernet gadget driver and use
those in 'linux/usb/composite.h'. The only difference is that now the
device name is printed instead of the ethernet interface name.

Tested using ethernet gadget on Jetson AGX Orin.

Signed-off-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Tested-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Link: https://lore.kernel.org/r/20230209125319.18589-1-jonathanh@nvidia.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "usb: gadget: u_ether: Do not make UDC parent of the net device"</title>
<updated>2023-02-09T12:18:24+00:00</updated>
<author>
<name>Paul Cercueil</name>
<email>paul@crapouillou.net</email>
</author>
<published>2023-02-09T10:56:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=bb07bd68fa0983e3915f83c471382868860389fe'/>
<id>bb07bd68fa0983e3915f83c471382868860389fe</id>
<content type='text'>
This reverts commit 321b59870f850a10dbb211ecd2bd87b41497ea6f.

This commit broke USB networking on Ingenic SoCs and maybe elsewhere.
The actual reason is unknown; and while a proper fix would be better,
we're sitting at -rc7 now, so a revert is justified - and we can work on
re-introducing this change for 6.3.

Fixes: 321b59870f85 ("usb: gadget: u_ether: Do not make UDC parent of the net device")
Signed-off-by: Paul Cercueil &lt;paul@crapouillou.net&gt;
Acked-by: Sascha Hauer &lt;s.hauer@pengutronix.de&gt;
Link: https://lore.kernel.org/r/20230209105626.10597-1-paul@crapouillou.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reverts commit 321b59870f850a10dbb211ecd2bd87b41497ea6f.

This commit broke USB networking on Ingenic SoCs and maybe elsewhere.
The actual reason is unknown; and while a proper fix would be better,
we're sitting at -rc7 now, so a revert is justified - and we can work on
re-introducing this change for 6.3.

Fixes: 321b59870f85 ("usb: gadget: u_ether: Do not make UDC parent of the net device")
Signed-off-by: Paul Cercueil &lt;paul@crapouillou.net&gt;
Acked-by: Sascha Hauer &lt;s.hauer@pengutronix.de&gt;
Link: https://lore.kernel.org/r/20230209105626.10597-1-paul@crapouillou.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: u_ether: Do not make UDC parent of the net device</title>
<updated>2022-11-09T11:39:33+00:00</updated>
<author>
<name>Sascha Hauer</name>
<email>s.hauer@pengutronix.de</email>
</author>
<published>2022-11-04T13:10:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=321b59870f850a10dbb211ecd2bd87b41497ea6f'/>
<id>321b59870f850a10dbb211ecd2bd87b41497ea6f</id>
<content type='text'>
The UDC is not a suitable parent of the net device as the UDC can
change or vanish during the lifecycle of the ethernet gadget. This
can be illustrated with the following:

mkdir -p /sys/kernel/config/usb_gadget/mygadget
cd /sys/kernel/config/usb_gadget/mygadget
mkdir -p configs/c.1/strings/0x409
echo "C1:Composite Device" &gt; configs/c.1/strings/0x409/configuration
mkdir -p functions/ecm.usb0
ln -s functions/ecm.usb0 configs/c.1/
echo "dummy_udc.0" &gt; UDC
rmmod dummy_hcd

The 'rmmod' removes the UDC from the just created gadget, leaving
the still existing net device with a no longer existing parent.

Accessing the ethernet device with commands like:

ip --details link show usb0

will result in a KASAN splat:

==================================================================
BUG: KASAN: use-after-free in if_nlmsg_size+0x3e8/0x528
Read of size 4 at addr c5c84754 by task ip/357

CPU: 3 PID: 357 Comm: ip Not tainted 6.1.0-rc3-00013-gd14953726b24-dirty #324
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x58/0x70
 dump_stack_lvl from print_report+0x134/0x4d4
 print_report from kasan_report+0x78/0x10c
 kasan_report from if_nlmsg_size+0x3e8/0x528
 if_nlmsg_size from rtnl_getlink+0x2b4/0x4d0
 rtnl_getlink from rtnetlink_rcv_msg+0x1f4/0x674
 rtnetlink_rcv_msg from netlink_rcv_skb+0xb4/0x1f8
 netlink_rcv_skb from netlink_unicast+0x294/0x478
 netlink_unicast from netlink_sendmsg+0x328/0x640
 netlink_sendmsg from ____sys_sendmsg+0x2a4/0x3b4
 ____sys_sendmsg from ___sys_sendmsg+0xc8/0x12c
 ___sys_sendmsg from sys_sendmsg+0xa0/0x120
 sys_sendmsg from ret_fast_syscall+0x0/0x1c

Solve this by not setting the parent of the ethernet device.

Signed-off-by: Sascha Hauer &lt;s.hauer@pengutronix.de&gt;
Link: https://lore.kernel.org/r/20221104131031.850850-2-s.hauer@pengutronix.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
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<pre>
The UDC is not a suitable parent of the net device as the UDC can
change or vanish during the lifecycle of the ethernet gadget. This
can be illustrated with the following:

mkdir -p /sys/kernel/config/usb_gadget/mygadget
cd /sys/kernel/config/usb_gadget/mygadget
mkdir -p configs/c.1/strings/0x409
echo "C1:Composite Device" &gt; configs/c.1/strings/0x409/configuration
mkdir -p functions/ecm.usb0
ln -s functions/ecm.usb0 configs/c.1/
echo "dummy_udc.0" &gt; UDC
rmmod dummy_hcd

The 'rmmod' removes the UDC from the just created gadget, leaving
the still existing net device with a no longer existing parent.

Accessing the ethernet device with commands like:

ip --details link show usb0

will result in a KASAN splat:

==================================================================
BUG: KASAN: use-after-free in if_nlmsg_size+0x3e8/0x528
Read of size 4 at addr c5c84754 by task ip/357

CPU: 3 PID: 357 Comm: ip Not tainted 6.1.0-rc3-00013-gd14953726b24-dirty #324
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x58/0x70
 dump_stack_lvl from print_report+0x134/0x4d4
 print_report from kasan_report+0x78/0x10c
 kasan_report from if_nlmsg_size+0x3e8/0x528
 if_nlmsg_size from rtnl_getlink+0x2b4/0x4d0
 rtnl_getlink from rtnetlink_rcv_msg+0x1f4/0x674
 rtnetlink_rcv_msg from netlink_rcv_skb+0xb4/0x1f8
 netlink_rcv_skb from netlink_unicast+0x294/0x478
 netlink_unicast from netlink_sendmsg+0x328/0x640
 netlink_sendmsg from ____sys_sendmsg+0x2a4/0x3b4
 ____sys_sendmsg from ___sys_sendmsg+0xc8/0x12c
 ___sys_sendmsg from sys_sendmsg+0xa0/0x120
 sys_sendmsg from ret_fast_syscall+0x0/0x1c

Solve this by not setting the parent of the ethernet device.

Signed-off-by: Sascha Hauer &lt;s.hauer@pengutronix.de&gt;
Link: https://lore.kernel.org/r/20221104131031.850850-2-s.hauer@pengutronix.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
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